U.S. Pat. No. 5,060,634 issued on Oct. 29, 1991 to Bruning et al. is one example of an ignition system for a heavy duty spark ignited internal combustion engine. The ignition system includes an ignition transformer assembly releasable connected to a terminal portion of a spark plug of such engine within a valve mechanism compartment. A spring member having a plurality of deflectable legs properly orient the ignition transformer within the valve mechanism compartment.
The design of U.S. Pat. No. 5,060,624 employs the traditional contact means or spring clips to establish electrical contact between the electrical source and the terminal portion of the spark plug. The arrangement does not accommodate for any variation in the axial length of the transformer assembly and spring clip due to manufacturing tolerances "stack-up" between the various parts within the valve cover. If the axial length is too long the contact means is forced against the terminal end of the spark plug which could result in cracking of the spark plug porcelain. If the axial length is too short a gap could result between the contact means and the terminal portion of the spark plug which would impede electrical conduction.
On spark ignited, internal combustion engines there are several types of connectors used to for making the electrical connection from the voltage source to the terminal portion of the spark plug. For many applications the existing art solves the problem. However, for many heavy duty engines the problem remains unsolved. Typically, the voltage source is connected to the terminal portion of the spark plug by a conductive spring clip connector that fits over the terminal portion. The spring clip connector typically has dimples that grip a groove of the terminal portion thereby mechanically securing the connector to the terminal portion for making electrical connection from the voltage source to the spark plug. While inexpensive to manufacture, the clamping force diminishes over time as metal relaxes and deforms due to vibration and high heat resulting in far less than optimum electrical conduit. This is exacerbated by the fact that many large stationary engines often run continuously. The gripping force is also effected by manufacturing tolerances of the spark plug terminal portion and the spring clip. The consequences of ignition failure are great, resulting in costly engine downtime and a lost production.
U.S. Pat. No. 5,322,394 issued Jul. 26, 1994 to E. L. Frost is one example of a spring clip connector that grips the terminal portion of the spark plug. This example also includes a spring which applies an axial spring force on the terminal end of the terminal portion for improved electrical. However, such axial force would tend to push the spring clip off of the terminal if not opposed.
The electrical connector system of the present invention eliminates the traditional spring clip. The electrical connector is so constructed and arranged that electrical contact is provided exclusively through a volute spring contacting the end of the terminal. A second spring axially biases the electrical conductor in a direction toward the volute spring to accommodate a variation is axial length due to tolerance between elements preventing damage of the components and insuring an electrical connection with the terminal portion of the spark plug.